In this proposal renal hemodynamics and volume homeostasis will be investigated in animals with abnormal pregnancies. Objectives of the proposed investigation are: a. Measure renal function and alterations in intravascular and extracellular volume during pregnancy in 1) Wistar rats with spontaneous hypertension (SH); 2) Animals with autologous immune complex disease affecting primarily the renal glomerulus; 3) Rats with chronic parenchymal kidney disease involving mainly the tubules. In each of these models blood pressure will be monitored prior to and during gestation. Clearances of inulin and its volume of distribution as well as PAH and its extraction and plasma volume will be measured in term gravid animals and simutaneously studied littermate (SH) or aged matched (renal disease) virgin controls. B. Evaluate the renal response to graded saline infusions in these 3 groups of rats with complicated gestation. Infusate volume will be calculated to expand animals by a volume equal to 10-20 percent of their anticipated inulin space, and filtered and excreted sodium will be measured during the 3 hours after the infusion. C. Survey effects of salt and repeated pregnancies on the course of gestations and the natural history of these diseases. Experiments will be performed after 3 successive pregnancies, as well as in rats ingesting high and low sodium diets. D. Establish morphological correlations with the observed pathophysiology in these models. Autopsies will include light and electron microscopical examinations, most specifically of the kindey (e.g. interstitial medullary cells in SH rats). Long term goals are to apply this information towards improving the management of human pregnancy complicated by hypertension or renal disease. BIBLIOGRAPHIC REFERENCES: Spargo, B.H., Lichtig, Ch., Luger, A.M., Katz, A.I., Lindheimer, M.D.: The renal lesion in preeclampsia. Examination by light, electron, and immunofluorescent microscopy, in Hypertension in Pregnancy. Lindheimer, M.D., Katz, A.I., Zuspan, F.P., eds., John Wiley & Sons, New York, 1976, pp. 129-138. Ehrlich, E.N., Nolten, W.E., Oparil, S., Lindheimer, M.D.: Mineralocorticoids in normal pregnancy in Hypertension in Pregnancy. Lindheimer, M.D., Katz, A.I., Zuspan, F.P., eds., John Wiley & Sons, New York, 1976, pp. 189-202.